[llvm] [LoopInterchange] Fix overflow in cost calculation (PR #111807)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

Is it possible to test this more targeted via an analysis test in `llvm/test/Analysis/LoopCacheAnalysis/`?

https://github.com/llvm/llvm-project/pull/111807